Postnatal adaptations of phosphatidylcholine metabolism in extremely preterm infants: implications for choline and PUFA metabolism

Evidence and Perspectives for Choline Supplementation during Parenteral Nutrition-A Narrative Review

Choline is an essential nutrient, with high requirements during fetal and postnatal growth. Tissue concentrations of total choline are tightly regulated, requiring an increase in its pool size proportional to growth. Phosphatidylcholine and sphingomyelin, containing a choline headgroup, are constitutive membrane phospholipids, accounting for >85% of total choline, indicating that choline requirements are particularly high during growth. Daily phosphatidylcholine secretion via bile for lipid digestion and very low-density lipoproteins for plasma transport of arachidonic and docosahexaenoic acid to other organs exceed 50% of its hepatic pool. Moreover, phosphatidylcholine is required for converting pro-apoptotic ceramides to sphingomyelin, while choline is the source of betaine as a methyl donor for creatine synthesis, DNA methylation/repair and kidney function. Interrupted choline supply, as during current total parenteral nutrition (TPN), causes a rapid drop in plasma choline concentration and accumulating deficit. The American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) defined choline as critical to all infants requiring TPN, claiming its inclusion in parenteral feeding regimes. We performed a systematic literature search in Pubmed with the terms "choline" and "parenteral nutrition", resulting in 47 relevant publications. Their results, together with cross-references, are discussed. While studies on parenteral choline administration in neonates and older children are lacking, preclinical and observational studies, as well as small randomized controlled trials in adults, suggest choline deficiency as a major contributor to acute and chronic TPN-associated liver disease, and the safety and efficacy of parenteral choline administration for its prevention. Hence, we call for choline formulations suitable to be added to TPN solutions and clinical trials to study their efficacy, particularly in growing children including preterm infants.

Is choline deficiency an unrecognized factor in necrotizing enterocolitis of preterm infants?

We undertook this review to determine if it is plausible that choline or phosphatidylcholine (PC) deficiency is a factor in necrotizing enterocolitis (NEC) after two clinical trials found a dramatic and unexpected reduction in NEC in an experimental group provided higher PC compared to a control group. Sources and amounts of choline/PC for preterm infants are compared to the choline status of preterm infants at birth and following conventional nutritional management. The roles of choline/PC in intestinal structure, mucus, mesenteric blood flow, and the cholinergic anti-inflammatory system are summarized. Low choline/PC status is linked to prematurity/immaturity, parenteral and enteral feeding, microbial dysbiosis and hypoxia/ischemia, factors long associated with the risk of developing NEC. We conclude that low choline status exists in preterm infants provided conventional parenteral and enteral nutritional management, and that it is plausible low choline/PC status adversely affects intestinal function to set up the vicious cycle of inflammation, loss of intestinal barrier function and worsening tissue hypoxia that occurs with NEC. In conclusion, this review supports the need for randomized clinical trials to test the hypothesis that additional choline or PC provided parenterally or enterally can reduce the incidence of NEC in preterm infants. IMPACT STATEMENT: Low choline status in preterm infants who are managed by conventional nutrition is plausibly linked to the risk of developing necrotizing enterocolitis.

A Narrative Review on Maternal Choline Intake and Liver Function of the Fetus and the Infant; Implications for Research, Policy, and Practice

Dietary choline is needed to maintain normal health, including normal liver function in adults. Fatty liver induced by a choline-deficient diet has been consistently observed in human and animal studies. The effect of insufficient choline intake on hepatic fat accumulation is specific and reversible when choline is added to the diet. Choline requirements are higher in women during pregnancy and lactation than in young non-pregnant women. We reviewed the evidence on whether choline derived from the maternal diet is necessary for maintaining normal liver function in the fetus and breastfed infants. Studies have shown that choline from the maternal diet is actively transferred to the placenta, fetal liver, and human milk. This maternal-to-child gradient can cause depletion of maternal choline stores and increase the susceptibility of the mother to fatty liver. Removing choline from the diet of pregnant rats causes fatty liver both in the mother and the fetus. The severity of fatty liver in the offspring was found to correspond to the severity of fatty liver in the respective mothers and to the duration of feeding the choline-deficient diet to the mother. The contribution of maternal choline intake in normal liver function of the offspring can be explained by the role of phosphatidylcholine in lipid transport and as a component of cell membranes and the function of choline as a methyl donor that enables synthesis of phosphatidylcholine in the liver. Additional evidence is needed on the effect of choline intake during pregnancy and lactation on health outcomes in the fetus and infant. Most pregnant and lactating women are currently not achieving the adequate intake level of choline through the diet. Therefore, public health policies are needed to ensure sufficient choline intake through adding choline to maternal multivitamin supplements.

Lactational Changes of Phospholipids Content and Composition in Chinese Breast Milk

Phospholipids are pivotal polar lipids in human milk and essential for infants’ growth and development, especially in the brain and cognitive development. Its content and composition are affected by multiple factors and there exist discrepancies in different studies. In this study, we determined five major phospholipids classes (phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, and sphingomyelin) in 2270 human milk samples collected from 0 to 400 days postpartum in six regions of China. The high-performance liquid chromatography coupled with an evaporative light scattering detector (HPLC-ELSD) was performed to quantify the phospholipids. Total phospholipid median (IQR) content was in a range between 170.38 ± 96.52 mg/L to 195.69 ± 81.80 mg/L during lactation and was higher concentrated in colostrum milk and later stage of lactation (after 200 days postpartum) compared with that in the samples collected between 10 to 45 days postpartum. Variations in five major sub-class phospholipids content were also observed across lactation stages (phosphatidylethanolamine: 52.61 ± 29.05 to 59.95 ± 41.74 mg/L; phosphatidylinositol: 17.65 ± 10.68 to 20.38 ± 8.55 mg/L; phosphatidylserine: 15.98 ± 9.02 to 22.77 ± 11.17 mg/L; phosphatidylcholine: 34.13 ± 25.33 to 48.64 ± 19.73 mg/L; sphingomyelin: 41.35 ± 20.31 to 54.79 ± 35.26 mg/L). Phosphatidylethanolamine (29.18–32.52%), phosphatidylcholine (19.90–25.04%) and sphingomyelin (22.39–29.17%) were the dominant sub-class phospholipids in Chinese breast milk during the whole lactation period. These results updated phospholipids data in Chinese human milk and could provide evidence for better development of secure and effective human milk surrogates for infants without access to breast milk.

Choline Kinetics in Neonatal Liver, Brain and Lung-Lessons from a Rodent Model for Neonatal Care

Choline requirements are high in the rapidly growing fetus and preterm infant, mainly serving phosphatidylcholine (PC) synthesis for parenchymal growth and one-carbon metabolism via betaine. However, choline metabolism in critical organs during rapid growth is poorly understood. Therefore, we investigated the kinetics of D9-choline and its metabolites in the liver, plasma, brain and lung in 14 d old rats. Animals were intraperitoneally injected with 50 mg/kg D9-choline chloride and sacrificed after 1.5 h, 6 h and 24 h. Liver, plasma, lungs, cerebrum and cerebellum were analyzed for D9-choline metabolites, using tandem mass spectrometry. In target organs, D9-PC and D9-betaine comprised 15.1 ± 1.3% and 9.9 ± 1.2% of applied D9-choline at 1.5 h. D9-PC peaked at 1.5 h in all organs, and decreased from 1.5-6 h in the liver and lung, but not in the brain. Whereas D9-labeled PC precursors were virtually absent beyond 6 h, D9-PC increased in the brain and lung from 6 h to 24 h (9- and 2.5-fold, respectively) at the expense of the liver, suggesting PC uptake from the liver via plasma rather than local synthesis. Kinetics of D9-PC sub-groups suggested preferential hepatic secretion of linoleoyl-PC and acyl remodeling in target organs. D9-betaine showed rapid turnover and served low-level endogenous (D3-)choline synthesis. In conclusion, in neonatal rats, exogenous choline is rapidly metabolized to PC by all organs. The liver supplies the brain and lung directly with PC, followed by organotypic acyl remodeling. A major fraction of choline is converted to betaine, feeding the one-carbon pool and this must be taken into account when calculating choline requirements.

Effects of Dietary Choline Levels During Pregnancy on Reproductive Performance, Plasma Metabolome and Gut Microbiota of Sows

This study investigated the effects of dietary choline levels during gestation on reproductive performance of sows. In addition, the plasma metabolome and gut microbiota of sows was studied. A total of 260 multiparous sows were allocated to five dietary treatment groups with increasing choline concentrations (1,050, 1,450, 1,850, 2,250, and 2,650 mg/kg) in a randomized complete block design. The sows were fed experimental diets from breeding until farrowing and a common lactating diet during lactation. The results showed that the backfat (BF) gain of sows during gestation, individual birth weight for total piglets born, piglets born alive, average piglet weight at weaning increased linearly (P < 0.05), whereas the within-litter birth weight variation coefficient (CV) of piglets born alive and suckling piglet mortality decreased linearly (P < 0.05) as dietary choline level increased. A quadratic effect of dietary choline level was observed for the average daily feed intake (ADFI) of sows during lactation (P < 0.05). ADFI was maximized when the dietary choline concentration reached 1,910 mg/kg. Plasma H₂O₂ concentration at day 30 of gestation in the 1,050 mg/kg group was greater than that in the 1,850 and 2,650 mg/kg groups (P < 0.05). Plasma metabolomics identified 46 metabolites among the three groups. Specifically, plasma concentrations of trimethylamine-N-oxide (TMAO), dopamine, and L-proline increased while 1-methylhistidine concentration decreased as dietary choline levels increased. In addition, bacterial observed species and richness (Chao 1 and ACE) at day 110 of gestation decreased as dietary choline levels increased (P < 0.05). For the gut microbiota composition, the enhanced dietary choline level decreased the abundance of phylum Proteobacteria (P < 0.05) and increased the abundance of phylum Actinobacteria (P < 0.05) at day 30 of gestation. Compared with the 1,050 mg/kg group, the abundance of genus Terrisporobacter was less in the 1,850 mg/kg group, and genera Bacillus and Cellulomonas were greater in the 2,650 mg/kg group. In summary, increasing dietary choline levels improved the birth weight, uniformity of neonatal piglets and litter performance during lactation. This may be associated with better antioxidant capability, metabolic status, and gut microbiota of sows during gestation.

Digestion and Absorption of Milk Phospholipids in Newborns and Adults

Milk polar lipids provide choline, ethanolamine, and polyunsaturated fatty acids, which are needed for the growth and plasticity of the tissues in a suckling child. They may also inhibit cholesterol absorption by interacting with cholesterol during micelle formation. They may also have beneficial luminal, mucosal, and metabolic effects in both the neonate and the adult. The milk fat globule membrane contains large proportions of sphingomyelin (SM), phosphatidylcholine (PC), and phosphatidylethanolamine (PE), and some phosphatidylserine (PS), phosphatidylinositol (PI), and glycosphingolipids. Large-scale technical procedures are available for the enrichment of milk fat globule membrane (MFGM) in milk replacement formulations and food additives. Pancreatic phospholipase A2 (PLA2) and mucosal phospholipase B digest glycero-phospholipids in the adult. In the neonate, where these enzymes may be poorly expressed, pancreatic lipase-related protein 2 probably has a more important role. Mucosal alkaline SM-ase and ceramidase catalyze the digestion of SM in both the neonate and the adult. In the mucosa, the sphingosine is converted into sphingosine-1-phosphate, which is both an intermediate in the conversion to palmitic acid and a signaling molecule. This reaction sequence also generates ethanolamine. Here, we summarize the pathways by which digestion and absorption may be linked to the biological effects of milk polar lipids. In addition to the inhibition of cholesterol absorption and the generation of lipid signals in the gut, the utilization of absorbed choline and ethanolamine for mucosal and hepatic phospholipid synthesis and the acylation of absorbed lyso-PC with polyunsaturated fatty acids to chylomicron and mucosal phospholipids are important.

Sphingolipidomics of serum in extremely preterm infants: Association between low sphingosine-1-phosphate levels and severe retinopathy of prematurity

BACKGROUND

Extremely preterm infants are at risk of developing retinopathy of prematurity (ROP) that can cause impaired vision or blindness. Changes in blood lipids have been associated with ROP. This study aimed to monitor longitudinal changes in the serum sphingolipidome of extremely preterm infants and investigate the relationship to development of severe ROP.

METHODS

This is a prospective study that included 47 infants born <28 gestational weeks. Serum samples were collected from cord blood and at postnatal days 1, 7, 14, and 28, and at postmenstrual weeks (PMW) 32, 36, and 40. Serum sphingolipids and phosphatidylcholines were extracted and analyzed by LC-MS/MS. Associations between sphingolipid species and ROP were assessed using mixed models for repeated measures.

RESULTS

The serum concentration of all investigated lipid classes, including ceramide, mono- di- and trihexosylceramide, sphingomyelin, and phosphatidylcholine displayed distinct temporal patterns between birth and PMW40. There were also substantial changes in the lipid species composition within each class. Among the analyzed sphingolipid species, sphingosine-1-phosphate showed the strongest association with severe ROP, and this association was independent of gestational age at birth and weight standard deviation score change.

CONCLUSIONS

The serum phospho- and sphingolipidome undergoes significant remodeling during the first weeks of the preterm infant's life. Low postnatal levels of the signaling lipid sphingosine-1-phosphate are associated with the development of severe ROP.

Choline Content of Term and Preterm Infant Formulae Compared to Expressed Breast Milk-How Do We Justify the Discrepancies?

Choline/phosphatidylcholine concentrations are tightly regulated in all organs and secretions. During rapid organ growth in the third trimester, choline requirement is particularly high. Adequate choline intake is 17–18 mg/kg/day in term infants, whereas ~50–60 mg/kg/day is required to achieve fetal plasma concentrations in preterm infants. Whereas free choline is supplied via the placenta, other choline carriers characterize enteral feeding. We therefore quantified the concentrations and types of choline carriers and choline-related components in various infant formulae and fortifiers compared to breast milk, and calculated the supply at full feeds (150 mL/kg/day) using tandem mass spectrometry. Choline concentration in formula ranged from values below to far above that of breastmilk. Humana 0-VLB (2015: 60.7 mg/150 mL; 2020: 27.3 mg/150 mL), Aptamil-Prematil (2020: 34.7 mg/150 mL), Aptamil-Prematil HA (2020: 37.6 mg/150 mL) for preterm infants with weights < 1800 g, and Humana 0 (2020: 41.6 mg/150 mL) for those > 1800 g, comprised the highest values in formulae studied. Formulae mostly were rich in free choline or phosphatidylcholine rather than glycerophosphocholine and phosphocholine (predominating in human milk). Most formulae (150 mL/kg/day) do not supply the amounts and physiologic components of choline required to achieve fetal plasma choline concentrations. A revision of choline content in formulae and breast milk fortifiers and a clear declaration of the choline components in formulae is required to enable informed choices.